How to make post right sidebar narrower

Would you please provide the link of your site?
It help me to address your problem easier.
Thanks

So sorry.

https://crazy8ministries.com/test/

HI there,

You can add this css in style.css file of child theme.

#st-right {
   margin-left: 50px;
   width: 100px;
}

You can change width and margin-left value as per your requirement.

Note: Please use child theme to add custom css so your changes will not be lost on theme update.

Thanks